Liquefaction of starch derived from cereal grains is utilized in the production of a variety of grain derived products. Grain-derived products include common food products such as breakfast cereals, pet foods and livestock feed, for example. Liquefaction of grain-derived starches is also used in the production of ethanol which is utilized in the production of combustible fuels the most common of which is gasohol, a 10% blend of grain derived ethanol with petroleum derived gasoline.
The production of ethanol in the United States has dramatically increased in recent years. The mandated use of oxygenates such as ethanol in gasoline by the Environmental Protection Agency's Renewable Oxygenate Requirement will result in further increases in the production of ethanol in the near future.
In order to produce ethanol from a cereal grain substrate, the grain substrate must be gelatinized, liquefied and saccharified before being fermented into ethanol which often includes enzymatic hydrolysis. The conversion of cereal grain starch into fermentable sugars consumes 30% of the total energy required for alcohol fermentation and is one of the major problems encountered the ethanol production industry.
Methods for converting a grain substrate into a liquefied starch solution are known in the art. The most commonly utilized method for starch liquefaction is jet steam cooking. However, jet steam cooking requires the grain substrate slurry, which is to be cooked, first have a minimum moisture content of 60-70% m.c.w.b. Because jet steam cooking requires such a high moisture content, the jet steam cooking process consumes a considerable amount of energy to heat the water contained in the starch slurry solution. However, reducing the moisture content of the starch solution in a jet steam cooker results in an output product that is difficult to pump and process due to very high viscosities. Further processing with enzymes is also very difficult at lower moisture contents using a jet cooker. Thus, there lies a need for a low energy consuming method of grain liquefaction the grain solution is processed with low moisture contents that results in a product suitable for enzymatic hydrolysis.